Try as they might, the Vietnamese just can't fathom backpackers. Why would someone who's obviously rich - and in a poor country where 20 US dollars a month is the average wage, every Westerner is rich - be so tight- fisted when it comes to ordering food and drink, and dress in such scruffy clothes?
Travellers are a funny lot. Note the use of the word "travellers". The neighbours going on their bargain package deal to Crete are tourists. We're travellers, we say, experiencing, not spoiling, a foreign culture. It's a big difference, we say. Yet when it comes down to it, many of us follow the herd.
Take the tendency that when we're far away from home, we suddenly feel the urge to dress in clothes we wouldn't normally be seen dead in. Go anywhere on the backpacking trail in Asia, and you'll feel like an outcast if you're not parading in a T-shirt and baggy patterned pants, with a friendship bracelet on your ankle and a bum-bag round your waist.
Then there's what we choose to do with our time, having travelled to the other side of the world. Instead of using local transport, most of us catch tourist minibuses from A to B. When we get there, we hang out in backpackers' bars and restaurants, drinking beer and fruit shakes, eating pancakes and stir-fried noodles, not even attempting to mix with the locals.
Mostly the Vietnamese just laugh and take our dollars, but sometimes they are offended by the way backpackers dress. Charlotte, 26, from Melbourne, southern Australia, is teaching English in Ho Chi Minh City. She's been living in Pham Ngu Lao, the bustling backpackers' district, for the past two years.
"What gets me is the skimpy vest tops and mini-skirts some of them wear: they flaunt their midriffs like they're out for a night clubbing in lbiza. It's just not suitable here, in a country where women still keep on their clothes to go swimming."
The real Vietnam has to be seen to be believed. But experiencing Vietnam isn't just about getting off the beaten track, although that's surprisingly easy - it's about doing what the young Vietnamese do. It's about di choi, which means cruising around after dark on a Honda Dream, posing in your coolest gear - fake Armanis, DM shoes, and rip-off designer label T-shirts a must.
It's about drinking Vietnamese coffee in huge open-air bars, lit with hundreds of tiny multi-coloured lights, to the strains of Abba or Boney M. Vietnamese musical taste is still in the 1970s. It's about catching a minibus with 20 other people and two chickens crammed into a space that should fit 10. It's about perching on child-sized plastic stools - definitely not for Western bottoms - eating pho or noodle soup for breakfast. But many Westerners miss out.
Ted, a worldly-wise American in his thirties, with an eagle tattoo on his left arm, draws heavily on his cigarette in Bar 333, Saigon (district 1 of Ho Chi Minh City) - yet another member of the expatriate brigade teaching English in Vietnam.
"Most of them haven't got a clue about anything. You'll see what I mean if you go to the Singh cafe early tomorrow morning: minibus after minibus waiting for backpackers. They call a register, and herd people into the buses. Singh cafe tours are for people who come to Vietnam once and say they've 'done Vietnam'."
I took his advice and got down to the Singh at six the next morning. Half an hour later the place was a heaving mass of rainbow-coloured loon pants, backpacks and "I've survived Saigon" T-shirts. Then the production line of buses started drawing up: Mekong Delta, Cu Chi Tunnels, Dalat, Nha Trang, Hue, Hoi An, Vung Tau, Hanoi. Two hours later, the place was a ghost town. At $7 for the trip from Saigon to Dalat, for example - twice the price you'll pay on a public bus - the cafe must be raking it in.
I found Charlotte, the English teacher again, having breakfast at Kim's cafe, another popular travellers' hangout.
"Many backpackers allow just two-and-a-half weeks for the Hanoi-to-Ho Chi Minh City run. That's no way near enough time. It's about the worst possible way to see Vietnam. They have a list: Thailand, Cambodia, Vietnam and China. Once they've ticked one country off on that list, they go on to the next one. Then they go and lose themselves in India".